The art is replete with surgical stapling instruments used for applying parallel rows of staples through compressed living tissue. These types of stapling devices are used, for example, in transecting or reconnecting intestinal, gastric and lung tissue.
One known surgical stapling instrument of this type is well known and is currently available under the trade designation "The ILA Stapler", catalog #3957 by Minnesota Mining and Manufacturing Company, St. Paul, Minn. The use of the stapler is described in the publication entitled "Surgical Stapling, Gastric and Small Bowel Procedures, Volume I", ISBN 0-937433-00-4, Library of Congress Catalog Number 85-082599 available from Minnesota Mining and Manufacturing Company, St. Paul, Minn. the contents of which is expressly incorporated herein by reference. The ILA Stapler and an improvement thereto is described in Redmond et al., U.S. Pat. No. 4,863,088 the entire specification of which is also herein expressly incorporated by reference. That stapling instrument comprises first and second elongate structural members each comprising a handle part and a jaw part projecting from a first end of the handle part. The structural members have pivot means at second ends of their handle parts adapted for free engagement and disengagement in a plane normal to the directions in which the members are elongate, which pivot means afford, when engaged, relative pivotal movement of the structural members in the plane between a closed position with the jaw parts in closely spaced relationship, and an open position spaced farther from each other than in the closed position. An elongate locking member having a pivot point closely adjacent a first end is mounted at its pivot point on the first end of the second structural member for pivotal movement around an axis generally normal to the plane between a locking position generally aligned with the handle part of the second structural member, and a release position with a second end of the locking member spaced from the second end of the second structural member. The first end of the locking member and the handle part of the first structural member adjacent its first end have surfaces adapted, when the pivot means are engaged and the structural members are in their open position, for engagement during movement of the locking member from its release position to its locking position to forcefully move the structural members to their closed position so that high compressive forces can be applied on tissues to be stapled between the jaw parts of the structural members. The stapler also comprises means adapted for releasable engagement between the elongate locking member and the second structural member which releasably hold the locking member in its locking position and thus maintain any compressive forces applied between the jaw parts. The stapling instrument is adapted to have a fixed or removable anvil positioned along one of the jaw parts, and a cartridge containing a plurality of staples disposed in rows positioned along the other of the jaw parts in opposition to the anvil, and the cartridge includes manually actuatable means for sequentially ejecting the staples from the cartridge to press the staples against the anvil to engage and close the staples in tissues between the jaw parts when the structural members are in their closed position. Additionally, if desired, the cartridge can include a knife that moves along and bridges between the cartridge and anvil to cut tissues between the rows of applied staples.
Existing "ILA" type staplers include a firing handle located on only one side of the surgical stapler handle along with a relatively large size jaw and a relatively small size jaw. These types of staplers and cartridge assemblies encounter problems when they are used in a medical procedure at a location in the patient's body where there is little room or clearance to maneuver or orient the surgical stapler. For example, in some procedures, the relatively small size jaw is placed through a slit-like incision in bowel tissue in order to be positioned adjacent to tissue to be stapled, and the larger jaw is placed through another slit-like incision in other bowel tissue. It is preferable to make these apertures as small as possible to minimize damage to the tissue. Existing staplers include a firing handle located only on one side of the surgical stapler and, since the position of the firing handle is dependent upon the location of the small jaw, the resulting position of the stapler is sometimes one in which access to the firing handle is restricted or even blocked by tissue (e.g. an organ). Thus, it is difficult for the surgeon to manually fire the stapler using the firing handle due to the obstructing tissue. Heretofore, attempts to solve this problem include using a long cylindrical rod placed against the firing handle to fire the stapler, but this is an undesirable solution as the use of such a rod for that purpose reduces the control the surgeon has over the firing of the stapler and creates a danger that the rod would slip off the firing handle and damage internal tissues.
Another problem associated with "ILA" type staplers is also encountered when the stapler is used in a surgical procedure at a cramped location where the surgeon's capacity to position the stapler is restricted due to the proximity of the stapler to sensitive tissue. Once the stapler has been oriented in the proper position, existing staplers use a lever locking member to clamp or approximate the tissue to be stapled between the stapler jaws prior to firing. Once the stapler is fired, existing lever locking members, such as the "ILA" stapler disclosed in U.S. Pat. No. 4,863,088 to Redmond et al., release the locking member by means of a button located on only one side of the stapler. Again, access to the button may be restricted or difficult if the stapler is used at a location in close proximity to sensitive tissue.
U.S Pat. No. 4,633,874 to Chow et al. discloses a latching mechanism including a latch arm which is movable to a partially latched position in which the jaw members are loosely connected together to permit the staple cartridge and anvil to be adjusted in position on the tissue without disconnecting the jaw members from each other. U.S. Pat. No. 4,520,817 to Green discloses a locking handle pivotable to cause camming surfaces to slide on lugs to thereby rotate frames toward each other about a pivot bar between open and closed positions. The prior art staplers disclosed in Chow et al. and Green disclose a locking mechanism generally referred to as an "over center" link and it is believed that such over center links are difficult to open when the stapler is used with thick tissue. Problems associated with opening the locking mechanism are only aggravated when the stapler is used at a cramped location.